Abstract: A magnetoclastic transducer for sensing a torque in a shaft (150) is formed by circumferentially magnetising a magnetisable, integral portion (156) of the shaft. To assist in the emanation of a flux-dependent torque, the transducer element portion (156) of the shaft may have further circumferentially magnetised portions (154, 158) to each side. These further portions (154, 158) are of opposite polarity magnetisation to that of the transducer element (156). The external magnetic flux emanated by the transducer (156) is a function of torque and is detectable by a magnetic field sensor (160). An alternative means for the same purpose is to provide the transducer element at a portion (172) of the shaft (170) having an integral annular section of raised profile projecting beyond adjoining portions of the shaft. The shaft may be provided with a series of circumferentially magnetised portions of alternating polarity.